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May 16, 2010 - Updated for a slightly different style and for the new items released. Also added some theorycrafting and updated some numbers that were changed with the recent patches in the comparisons.

What's in this guide?
First thing's first. This guide assumes you already know how to play Rammus, or can easily pick up on it. The only thing I will cover is the difference between the normal Rammus you've seen and AP flavored Rammus. If you want a guide to tell you how to actually play Rammus, pay a visit to one of the many other guides on him, or try him out yourself!

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--AP Rammus? Are you some kind of noob?
--But Rammus is supposed to be a tank!
--What summoner spells should I get?
--What masteries should I get?
--What runes should I get?
--What skills does Rammus have, and how do they work?
--What order should I learn his skills?
--What items should I get?
--How is the playstyle different from normal Rammus?
----Early Game
----Mid Game
----Late Game
--Got any tricks for me?
--What was the point again?

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AP Rammus? Are you some kind of noob?
AP is a strong choice on many champions because it scales their spells, and normally burst damage is what wins fights. AP scales all of Rammus's damaging abilities, and they have excellent ratios. I'll go into more detail on the ability scaling in the appropriate section. The real strength of this is the fact that it's much easier to get defensive stats on AP items than on physical items, and the tank items in normal Rammus builds often sacrifice health. With an AP build, you get massive damage, health, and Armor/Magic Resist all rolled into one! AP Rammus is one of those builds that looks like it won't work, but it actually works surprisingly well.

But Rammus is supposed to be a tank!AP Rammus still is a tank. It is a common misconception that AP builds and casters in general are squishy. Some of the best AP items give important survivability stats. In fact, in most cases, good AP items give needed health that many armor and magic resist items don't have.

Some math on the subject:
[quote]The Armor/MR thing: It's true that armor/MR increases your effective health based off of a percentage of total health per 100 Armor/MR. However, at a certain point, armor/MR is no longer the most effective way to increase effective health.

But remember, Rammus has DBC, giving him a bonus 150 Armor and MR... so let's redo these calculations.

With DBC, you have roughly 6580.99 effective physical health with no items, roughly 5549.76 effective magic health with no items, and 6065.38 total effective health.

By adding 100 Armor, you have 8548.99 effective physical health, 7049.38 total effective health.
By adding 100 MR, you have 7537.44 effective magic health, 7059.22 total effective health.
By adding 860 health, you have 9456.83 effective physical health, 7974.96 effective magical health, and 8715.9 overall effective health -- which is already the threshold where the same cost in health beats the same cost in armor. The magic resist is much more expensive.

So while using DBC, you've already passed the threshold where health is better than armor/MR. In addition, almost every source of damage in this game is magical in nature, meaning that armor is less effective than MR. In addition, your armor can get pierced in large quantities, but your health cannot. Bloodrazor is reduced by MR -- which is one of the main focuses of this build.

What else does this build feature?
If the enemy team isn't packing mass disables or massive magic damage, we'll be picking up Boots of Mobility instead of Boots of Swiftness or Ninja Tabi/Merc Treads. Why? Massive travel speed, and to turn your Powerball into a tactical nuke. For this build, you need to master using Powerball. No questions, no excuses, just do it. Be able to weave in and out of creeps. Be able to avoid new waves entirely. You know how fast Yi is with Highlander up? Turns out, with this build, you can catch him, easily. Lastly, this build also features maximum cooldown reduction, allowing Rammus to spam all his skills quickly. It ultimately reduces their times to 7.2 seconds on powerball, 10.8 seconds on Ball Curl, 5.4! seconds on Taunt, and 36 seconds on Tremors.

What are its weaknesses?
Depending on your item choice, earlygame you could be lacking in armor or magic resist while ball curl isn't up. In addition, a lot of your best damage is magic damage, so Magic Resist will reduce your effectiveness. By getting Boots of Mobility, you'll be sacrificing some in-combat movespeed for fast travel time and high speed powerballs. The only thing that will screw you up is when someone casts a slow on you during powerball -- your speed will drop MASSIVELY. You'll lose both the Mobility bonus and be further slowed. You might still catch up, but it will take you longer. Lastly, max cooldown reduction means that once you finish your build, the golem buff will lose part of its effectiveness.[/quote]

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What summoner spells should I get?Required
--Flash - Start up powerball. -> The enemy lawls because you're behind your creeps. -> Flash into them. -> ??? -> Profit. Can also be used for easymode ganks
--Lowbie Alternatives - Ghost is a decent choice. The only problem is this summoner spell should be used for ezmode powerball lulz, and ghost is meh for it. Sure you get a speed boost, but you can't dodge creeps with it, and you can't flash into an enemy team to AoE stun everyone at once.Reccommended
--Clarity - The mana regen is really nice at all stages of the game, especially since Rammus's mana pool begins so low. Also, your lane partner will thank you for picking this up. It allows for much more aggressive play from you both.
--Cleanse - The only problem with Rammus is if he's slowed, he has a hard time doing anything. This will aid that.
--Ghost - While the earlier slot wasn't quite what we wanted from Ghost, Ghost is a strong choice for the second spell. It allows you to maintain a high speed even outside of powerball, and allows for easy initiation when powerball would not be the best choice.Optional
Anything that will help you out, honestly. Teleport works well, as does Exhaust. Fortify if you really want it, it can be decent if you use it while taunting, but that's more for lulz than actual good gameplay.

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What masteries should I get?0/21/9 or 9/21/0Why? - Defensive masteries help you to survive against burst, along with the Cleanse mastery if you choose to get it, or Fortify if that strikes your fancy. Go 9 in Utility for Teleport or Clarity in addition to the mana regen and experience boost. Go 9 in Offense if you picked up Exhaust for the boost to that as well as the cooldown reduction and spell pen.

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What runes should I get?
The thing to remember when choosing runes is that unless you stack certain ones, they have almost no effect on lategame. The runes you'll be choosing will mostly be to add onto your role and to help mitigate some of your item-dependant weaknesses.

Red - Depends on what you like. If you want more earlygame damage potential, get AP. If you want to maximize effectiveness, get Magic Pen. If you want to maximize movespeed and be a little tankier, get dodge.Yellow - Dodge is probably best. If for some reason you don't think so, get Health.Blue - Magic Resist per level. This gives you a reasonable buffer against magic damage that becomes better than static MR runes around level 9, which is around the time magic burst starts happening.Quintessence - Dodge/Health, AP, MR per level, or Magic Pen.

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What skills does Rammus have, and how do they work?
[quote]--Passive: Spiked Shell - Rammus gains additional damage as his shell becomes reinforced, converting 25% of his armor into damage.
--What's the deal? - We'll still be benefiting from this passive, just not as much as a straight armor build. It's not as strong as people make it out to be either. Most of the bonus damage you get from this is from Ball Curl and passive armor gain, NOT from your items! A normal Rammus build will go for 2x Sunfire Capes and a Guardian Angel. Even after you get all three, most of your damage still comes from passive armor gain coupled with Ball Curl! Rammus will have roughly 80 armor at max level, and Lv5 Ball Curl gives 150. This is a total of 230. 2x Sunfire Capes plus Guardian Angel is only 45 x2 + 68 = 158. Those items only give Rammus an extra 40 damage! You may be thinking, "But Sunfire Capes give an AoE DoT effect!" Well my friends, read on, you'll learn much.

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--Q: Powerball - Rammus accelerates in a ball towards his enemies, dealing 100/150/200/250/300 (+1 per ability power) magic damage and causing 28/36/44/52/60% reduced movement speed to nearby enemies on impact.
--What's the deal? - Ah yes, Powerball. This is Rammus's main skill, and by far his most devastating, with this build. The main thing I would like you to notice is the fact that it has a 1:1 AP ratio. I'll sum this up for you. The only non-ultimate AoE skill with a 1:1 ratio that I can think of other than Powerball is Veigar's Dark Matter, and Powerball is much easier to land, and it affects a larger AoE. Imagine dealing 600-800 damage to 5 enemy champions in one shot. Sound nice? Well, read the next skills and find out how much they add to the damage. Like I said before, learn to use this skill like a pro. If you don't, you will not win as AP Rammus.

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--W: Defensive Ball Curl - Rammus goes into a defensive formation for 6 seconds, increasing his armor and magic resistance by 50 / 75 / 100 / 125 / 150 and returning 26 / 32 / 38 / 44 / 50 (+0.25 per ability power) magic damage to attackers.
--What's the deal? - This skill is the hard counter to Yi and Tristana. I've also used it to save my life many times in the lane when I'm being hit by spells. This skill will not scale at all with armor or physical damage stats, only with AP, and wow, it scales well. 0.25:1 is a nice ratio for this skill. At 220 AP, which is around where you should end up in any normal game, you'll be returning 55 bonus damage, which is more than double its base return at max level. At 300 AP, which is your ideal number in a game where you have to stay tanky, it returns a bonus 75 damage, which effectively multiplies the damage return on this skill by 2.5. Think, you damage enemy champions for 105-125 damage every time they hit you. Sword of the Divine only adds 100 bonus damage every four attacks. Compared to that, this skill does **** fine.

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--E: Puncturing Taunt - Rammus taunts the unit into a reckless assault, reducing their armor by 10 / 15 / 20 / 25 / 30 and forcing them to attack Rammus for 1 / 1.5 / 2 / 2.5 / 3 second(s).
--What's the deal? - On first look, this skill hasn't changed by switching to AP. But because of the changes to Ball Curl and Tremors, Taunt is a much stronger ability. Not much else to say about it.

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--R: Tremors - Rammus creates tremors beneath him, dealing 65/130/195 (+0.3 per ability power) magic damage per second to nearby units and structures.
Lasts 8 seconds.
--What's the deal? - Rammus's ulti. Now here's a place where the bonus AP really shines. A 0.3:1 ratio may not sound that good, but you have to remember, that's 0.3:1 per second. Over the entire course of the skill, that's a 2.4:1 ratio. You won't always get to deal full damage, but when you can trap a champion, it becomes painful fast. At 240 AP, that's 1560 + 576 = 2136 magic damage. At 300 AP, that's 1560 + 720 = 2280 magic damage over 8 seconds! At 300 AP, the bonus damage added here beats out 2x Sunfire Capes by 10 damage per second. Not much right? Wrong. This bonus damage also affects buildings. Add in a Sivir and you have one of the strongest lane pushing combos in the entire game. Endgame, Rammus can easily tank towers while his ulti is up shredding it to pieces.
Note: As a comparison, Anivia's ulti scales with a 0.25 ratio, which is less than Rammus's, and Fiddle's ulti scales with a 0.35 ratio over 5 seconds, or a 1.75:1 ratio over the entire course of his ultimate, which is MUCH less than Rammus's total scaling. Rammus's ulti also affects buildings, unlike Fiddle's ulti.

Why get Powerball first?
The slow and damage will help tremendously at early levels, much more so than a 1 second disable or a little extra Armor/MR.

Why the weird leveling on Powerball?
The AP scaling remains the same at all levels, and you only really need the bonus damage from leveling the skill up to the third rank. The slow is a nice slow, but it's not that necessary to max it over your other skills. Besides, you'll have Rylai's as well as Randuin's Omen.

Why an early rank of Ball Curl?
It deals nice damage. No, really. You get bonus damage from the armor it gives, and anyone attacking you gets a minor damage return. Nothing major, but early on every little bit counts, and it can also help a lot in a tough lane by increasing both your armor and magic resist by a decent amount. 50 armor and magic resist at that low level is substantial.

Ball Curl at Lv3 or Lv5?
That depends on whether your lane is difficult or not. If you find yourself being attacked more often, having Ball Curl can be extremely helpful. If your lane is dominant, it's not worth delaying Lv2 Powerball to get Ball Curl at Lv3.

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What items should I get?

At the StartMana Gem - Rammus needs mana so he can use his skills more in the lane.2x Health Potion - Self explanitory. Helps you stay in the lane longer.

-OR-

Doran's Ring - A small amount of AP and mana regen as well as some health. It's more effective to be able to use your skills more often and more effectively than it is for you to gain extra armor and HP regen like you would get from the Shield.1x Health Potion - Self explanitory. Helps you stay in the lane longer.

Which Boots?Boots of Mobility - Already explained earlier, but I'll recap it. Helps you run around the map faster, especially if you use Powerball to get around. It also means you can chase anything down if they don't focus on hitting you every 5 seconds to cancel your movespeed bonus. Even then, if they keep doing that, they'll be easier to catch because they keep turning around.Merc Treads - If the enemy team is heavy in disables or has massive (and I mean massive) magic burst, Mercs are important for both more survivability and less time unable to do anything.When do I get boots?
Fairly early. I usually get Lv1 boots on my first fountain trip. I'll also upgrade them after my first Catalyst.

Which is my first big item?
Trick question. Your aim at the start won't be to get your first item. Your aim will be to judge what items you will need later on down the road.Get a Catalyst - No matter what happens, you'll probably want to get one of these before you decide on what your item build will be. After you get this, focus on figuring out if you'll be taking more magical or physical damage, and remember this.Crossroads - The next item to grab is where you make your decision. If they'll be dealing some major magic damage, grab a Negatron Cloak. If they'll be dealing little to no magic damage, get your Heart of Gold now.

Tank time! - This is where you'll start building yourself up. Heart of Gold if you haven't. Afterward, you should focus on finishing your Rod of Ages. Once you get these, you'll notice a significant difference in your tankyness, as well as in your damage output and mana pool. Once you get these items, you'll really start to shine.

Okay, now what? - Next you have another decision to make. If they're dealing a lot of magic damage and if you grabbed a Negatron Cloak earlier, or if they're not dealing a significant amount of damage at all, now's the time to build your Rylai's Scepter; if they're dealing a significant amount of physical damage, finish your Randuin's Omen.

Now we're rolling! - Your next job will be easy. If you don't have your Randuin's Omen, build it. If you don't have your Rylai's, build it.

Almost home - Your item build should be almost complete. If you grabbed a Negatron Cloak, you have a choice to make. If you're being targeted by key spells or disables, upgrade it into a Banshee's Veil. Otherwise, build it into an Abyssal Scepter. If you haven't grabbed your Glacial Shroud, do so. If you have an open slot at this point, you can get whatever fits best. Abyssal Scepter if you're after more MR and damage, grab a second Rylai's if you want some health and damage along with the ability to slow for a slightly higher amount.

And the finishing touch! - The very last thing you should do no matter what choice of build you picked should be upgrading your Glacial Shroud into a Frozen Heart. You will almost never reach this step.

What if I don't need to have this much health? - If you don't need this much health, you must have reached the point where you have a free slot. Feel free to use something more damaging. Lichbane is nice because of the movespeed and bonus damage on attack. Zhonya's Ring is nice for the bonus AP and the active effect. I warn you though, this will almost never happen in a real game. You are a tank, your job is to tank. You're not meant to be an awesome AP carry with 800 AP.

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How is the playstyle different from normal Rammus?Early Game
Played mostly the same, except with Flash you can get easier First Bloods than many other lanes can. Other than that addition, not much else differs. Harass, use Taunt + Powerball for first blood, and in general dominate your lane.Mid Game
This is where your playstyle really changes. Normally Rammus would be farming lanes at this point, trying to work up enough gold for his first sunfire cape. This is not your style for AP Rammus. Your job is to run from lane to lane, initiating ganks for your allies! Your skills make your team exteremely dominant in team fights, and at this point you should be fairly tanky. If you need some gold, you should be able to clear entire creep waves with Powerball.Late Game
This is where you'll shine. At this point, you should have some nice AP to back up your skills, and you should have enough health and mitigation to tank a lot before going down. You should be doing one thing here: pushing with your team. You're still a dominant force in team fights, and with the AP you should be packing, you're a threat to their entire team with Powerball + Tremors. If you've just won a team fight or if you're just looking to down a tower, feel free to use Tremors on towers -- It's very effective! Also note that at this point Powerball should be oneshotting entire creep waves, making you some easy gold as well as making you a strong pusher! If you've been doing well assisting your team, you should be able to push to win easily at this point. GG, you've just completed your first game as AP Rammus!

Is this a viable solo?
Anything can be a viable solo if the player knows what he's doing, but picking up a solo lane is not what this guide intends you to do. Your main job is to be the tank! That entails initiating team fights, and helping your allies gank. Your earlygame ganking potential is wasted if you don't share a lane!

What KDA should I expect from this build?
The aim of this build isn't to get a massive amount of kills, it's to maximize your team effectiveness while allowing you to tank and farm well. My worst game as AP Rammus, I went roughly 3/8/10. My best game as AP Rammus I went roughly 10/2/13. Your KDA will mostly depend on how well you work, how strong your team is, and how good your opponents are at countering you and your team. However, you should have more assists than kills.

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Got any tricks for me?
Most of them are Rammus tricks in general, but sure, I'll share them.Learn how long Powerball lasts. - This is vital. You need to learn how fast you can move, how long it will last, and adjust yourself accordingly. An old standby is to charge up powerball while in brush and run up to them from the brush at 700-900 movespeed.Learn Powerball's hit box. - This is extremely important, especially if you want to position Flash. Ideally, you'll want to Flash in front of them to knock them back toward your allies.Powerball doesn't interrupt channeling! - This is somewhat important. I'm sure you don't want to powerball into Nunu only to find out that his ulti will continue to charge up to full strength anyway and chop your health down by 2/3.Taunt under towers! - This one is easy to learn on your own. It's simple. If an enemy champion attacks you under your tower, the tower targets them. Taunt makes an enemy champion attack you for 1/1.5/2/2.5/3 seconds. This makes the tower have free hits on them for 1/1.5/2/2.5/3 seconds. Very useful for grabbing kills if they push to your towers.If you can, try to finish with Powerball! - Later on when you have enough cooldown reduction, you can both initiate and finish with Powerball. The reason you want to finish with it is because with AP, it deals massive damage in a burst, so it leaves them less time to figure out that they're gonna die and run.Run beside champions, don't attack! - If an enemy champion is running away and you have your ulti up, don't autoattack them unless you know you're much faster. Your ulti will do much more damage than autoattacks, and you're better off being sure all 8 ticks hit.Taunt and run! - Taunt someone and run toward your tower/team. It makes it so the enemy will run in the opposite direction he wants to, which is away from you. It also will give you slightly more distance you can safely chase, which can mean all the difference.

What was the point again?
The main point of this guide is to point out the fact that AP Rammus seems to outshine the other Rammus builds by a fair margin. At first, AP Rammus started out as a joke within my circle of friends. However, one day after playing another tanky AP champion I thought, "AP on Rammus might not be so bad afterall." So we tried it in a few ATs. Normally we do well, but we never did this well. We steamrolled them. I've played other Rammus builds and done well. But as AP Rammus, it's just so much easier. One of the best parts of this build is the ease with which you gain HP as well as damage, which helps a lot during the early stages of the game. As AP Rammus, I find myself getting at least 1/2 to 2/3 of my item build consistantly, whereas with other Rammus builds I would have a hard time getting 1/3 of it before the game ended.

This was originally supposed to be the ace up our sleeve, but my friends all agreed that we should spread the word. The days of stacking Sunfire Capes are over.

--Please, if you have anything you'd like to input, feel free to post here or PM me. I'd prefer if only constructive posts were made.

That is what i needed to give rammus another run.
Already played a game and i liked it a lot (although i need to be used with powerball again)
the only con is that i found it very squishy early game, but maybe it is just me sucking at it =/
Great guide

This is an appropriate alternative choice to the common Rammus build, but it would be wrong to say it will "outshine" other rammuses. This is a kill build. Your never going to be much of a tank and have problems dealing with heavier heroes throughout the game. Definitely usable, but superior? no

@Feign: How are you never going to be much of a tank? With the build, you have around 3100 health as well as ~190 armor and if you grab the Abyssal Scepter you'll have ~90 Magic Resist. The main point of switching Magic Resist and Armor to health for this build is because Ball Curl already gives a massive amount -- way more than is actually needed, and it approaches the point where it has little bonus effect. When using this build, you should pretty much always have Ball Curl up when you need it, too. Leaguecraft puts his effective health at 5800 magic and 9000 physical, not counting Ball Curl. Not only that, but this Rammus is actually a threat, meaning people have an incentive to attack him instead of your allies, which is the main purpose of a tank. And as for having problems with heavier champions? I've never had any problems dealing with anything other than massive amounts of magic damage before I get my magic resist. And hey, other Rammus builds have trouble with magic damage too. In fact, they have more trouble than this build. Common Rammus may be able to deal better with physical damage, but this one deals much better with magical damage and when your armor gets around 250, more armor gives little benefit compared to health.

@Toddy: Depends on what you mean by earlygame squishyness. Even with common builds Rammus is fairly squishy earlygame. In fact, he does have one of the lowest health gains of all the tanks, which is why we try to remedy this early. If you feel that you're too squishy earlygame, finish the Catalyst before getting boots.

@Feign: How are you never going to be much of a tank? With the build, you have around 3100 health as well as ~190 armor and if you grab the Abyssal Scepter you'll have ~90 Magic Resist. The main point of switching Magic Resist and Armor to health for this build is because Ball Curl already gives a massive amount -- way more than is actually needed, and it approaches the point where it has little bonus effect. When using this build, you should pretty much always have Ball Curl up when you need it, too. Leaguecraft puts his effective health at 5800 magic and 9000 physical, not counting Ball Curl. Not only that, but this Rammus is actually a threat, meaning people have an incentive to attack him instead of your allies, which is the main purpose of a tank. And as for having problems with heavier champions? I've never had any problems dealing with anything other than massive amounts of magic damage before I get my magic resist. And hey, other Rammus builds have trouble with magic damage too. In fact, they have more trouble than this build. Common Rammus may be able to deal better with physical damage, but this one deals much better with magical damage and when your armor gets around 250, more armor gives little benefit compared to health.

well, 190 armor isnt much compared to 400 armor most people end up with late game with the usual rammus build. Over 400 armor is not too much armor when faced with a good amount of physical characters late game. As for boosting MR, well, if you are a smart player you will adjust accordingly and get MR when needed. End game, most people expect rammus to go out into the fray first and absorb much of the damage, your build isnt viable for that. Again, didnt say your strategy was bad, its an interesting alternative, but for over all game purposes- pushing, ganking, tanking- you cant claim your build is superior.

well, 190 armor isnt much compared to 400 armor most people end up with late game with the usual rammus build. Over 400 armor is not too much armor when faced with a good amount of physical characters late game. As for boosting MR, well, if you are a smart player you will adjust accordingly and get MR when needed. End game, most people expect rammus to go out into the fray first and absorb much of the damage, your build isnt viable for that. Again, didnt say your strategy was bad, its an interesting alternative, but for over all game purposes- pushing, ganking, tanking- you cant claim your build is superior.

Actually Feign, the more armour you have, the less useful it becomes. One thing this guide emphasizes, is that the best way to tank is to mix armour and HP. To give you an idea of what I mean, if memory serves, 100 armour is 50% reduction. I think it's around 250 or so, maybe higher for 75%. Beyond that, it pretty much doesn't increase. The only potential use of armour higher than that, is as a buffer to fight against arnour penetration. Each point of health at the 50% value, and the 75% value are effectively worth that much more against physical attackers.

Aditionally, this build allows for more magic resistance, and gives a magic penetration aura, meaning not only do you take less damage from spells, his main weakness, but you also deal more with your skills if they don't buy magic resist, and aid any spellcasters on your side. If they buy magic resist just to counter you, your carry will destroy them.

This also adds an element of fear, like many high damage, high burst builds. People start to lose common sense when they see the powerball coming their way, but with good reason. The sheer amount of AoE damage you can manage while maintaining more tankiness than a typical armour based build is amazing.

Do not forget that Cho'Gath and Singed, as well as Amumu can all be played as very, very effective AP tanks. This is due to AP items giving a lot of health, as well as buying one armour item, and one magic resist item. However, they don't have a skill that boosts your armour and magic resist by 150 that you can use every 10 seconds or so, so you will be more tanky than them.

Actually Feign, the more armour you have, the less useful it becomes. One thign this guide emphasizes, is that te best way to tank is to mix armour and HP. To give you an idea of what I mean, if memory serves, 100 armour is 50% reduction..

Depends on how you view it. In terms of damage reduction % sure. As the forula works you can never hit 100% reduction.

This is how I look at it. But yes there is a balance, because once you start getting 500+ armor, you have to think any +health or +regen item you get is x5 as effective. So I see it as armor doesn't get less effective, it just makes health items more effective.

Actually Feign, the more armour you have, the less useful it becomes. One thign this guide emphasizes, is that te best way to tank is to mix armour and HP. To give you an idea of what I mean, if memory serves, 100 armour is 50% reduction. I think it's around 250 or so, maybe higher for 75%. Beyond that, it pretty much doesn't increase. The only potential use of armour higher than that, is as a buffer to fight against arnour penetration. Each point of health at the 50% value, and the 75% value are effectively worth that much more against physical attackers.

Aditionally, this build allows for more magic resistance, and gives a magic penetration aura, meaning not only do you take less damage from spells, his main weakness, but you also deal more with your skills if they don't buy magic resist, and aid any spellcasters on your side. If they buy magic resist just to counter you, your carry will destroy them.

This also adds an element of fear, like many high damage, high burst builds. People start to lose common sense when they see the powerball coming their way, but with good reason. The sheer amount of AoE damage you cn manage while maintaining more tankiness than a typical armour based build is amazing.

Do not forget that Cho'Gath and Singed, as well as Amumu can all be played as very, very effective AP tanks. This is due to AP items giving a lot of health, as well as buying one armour item, and one magic resist item. However, they don't have a skill that boosts your armour and magic resist by 150 that you can use every 10 seconds or so, so you will be more tanky than hem.

do you know the exact number where armor deduction caps? Do you have any resources to back that? If this is true, it certainly would be something to consider